- Chapter15 Key
197. Fast twitch muscles
*a. show little facilitation and are often used phasically.
b. show considerable facilitation and are often used phasically.
c. show little facilitation and are often used tonically.
d. show considerable facilitation and are often used tonically.
198. Which of the following is characteristic of vertebrate "fast twitch"
muscle fibers?
a. They are the predominant fiber type in tonic-type muscles.
b. They often show considerable facilitation.
c. They are fatigue resistant.
*d. They usually produce action potentials.
199. Slow twitch muscle in a vertebrate
a. has a relatively weak contraction.
b. shows considerable facilitation.
c. is often tonic in action.
*d. is all of the above.
200. Which of the following is characteristic of invertebrate "slow twitch"
muscle fibers?
a. They usually produce action potentials.
b. They show little facilitation.
c. They are the predominant fiber type in muscles used mainly in
phasic-type actions.
*d. They are fatigue resistant.
201. Slow twitch muscle usually shows
a. strong contraction.
*b. considerable facilitation.
c. large, overshooting electrical responses.
d. low resistance to fatigue.
202. The most simple innervation of a mammalian muscle will probably be
*a. uniterminal, unineuronal.
b. polyterminal, unineuronal.
c. uniterminal, polyneuronal.
d. polyterminal, polyneuronal.
203. The innervation of mammalian fast-twitch muscle is usually
*a. uniterminal, unineuronal.
b. polyterminal, unineuronal.
c. uniterminal, polyneuronal.
d. polyterminal, polyneuronal.
204. The most complex innervation of cat muscle in an appendage will probably
be
*a. uniterminal, unineuronal.
b. polyterminal, polyneuronal.
c. uniterminal, polyneuronal.
d. polyterminal, unineuronal.
205. Fast twitch muscle fibers in vertebrate animals tend to be innervated in a
______ fashion.
a. polyneuronal, uniterminal
b. polyneuronal, polyterminal
*c. unineuronal, uniterminal
d. unineuronal, polyterminal
206. Partly because arthropod muscle cannot conduct action potentials, the
SIMPLEST innervation of this muscle is
a. uniterminal, unineuronal.
*b. polyterminal, unineuronal.
c. uniterminal, polyneuronal.
d. polyterminal, polyneuronal.
207. The most complex innervation of insect muscle in an appendage will
probably be
a. uniterminal, unineuronal.
b. polyterminal, unineuronal.
c. uniterminal, polyneuronal.
*d. polyterminal, polyneuronal.
208. One would expect to find a muscle fiber that does not conduct action
potentials to have polyterminal innervation because
a. the presence of more than one motor neuron innervating a muscle
increases the flexibility with which the muscle can be used.
b. only muscle fibers that cannot generate APs could distinguish between
the synaptic action of different motor neurons.
c. multiple epps interfere with the generation of APs.
*d. multiple synapses would ensure that all parts of the muscle fiber
membrane were adequately depolarized so that effective contraction
could occur.
209. In a human biceps muscle, each muscle fiber is innervated by
a. a different axon.
b. the same axon.
c. several different axons.
*d. an axon that also innervates some other (but not all) muscle fibers.
210. A motor unit is
a. a group of muscles that work together.
b. two groups of muscles that work in opposition to each other.
*c. all the muscle fibers in a muscle innervated by a single motor neuron.
d. all the muscles in a limb innervated by a single nerve.
211. A motor unit is a motor neuron and
a. the muscle it innervates.
b. all the other motor neurons with which it is normally active.
*c. all the muscle fibers it innervates.
d. the parts of the muscle that functionally act as a unit during some
movement.
212. Suppose a vertebrate muscle has 1,000 muscle fibers and the nerve
innervating the muscle contains 100 motor neurons, each motor neuron
innervating 10 muscle fibers with no overlap. The number of motor units in
this muscle is
a. 1.
10.
b. *c. 100.
d. 1,000.
213. Muscles with few motor units, and both polyterminal and polyneuronal
innervation, are characteristic of
a. mammals mainly.
b. most vertebrates.
c. insects mainly.
*d. most invertebrates.
214. "Control by recruitment" in a muscle refers to
a. regulation of tension by variation in the frequency of firing of
individual motor units.
b. the use of the size principle to control force.
*c. regulation of tension by variation in the number of motor units that
are active.
d. the use of a matching of muscle and nerve properties to control muscle
force.
215. Recruitment, a means of increasing muscle force, works through
a. an increase in the number of vesicles of acetylcholine released by the
motor neuron.
b. activity in additional gamma motor neurons to boost the action of the
alpha motor neurons.
c. an increase of rate of firing in the motor neuron to cause more muscle
fibers in each motor unit to be active.
*d. activity in additional alpha motor neurons, thus increasing the number
of active motor units contributing to the force.
216. Increase of tension in a cat's muscle is accomplished by
a. increasing the frequency of firing of all the motor units.
*b. recruitment of additional motor units as higher tensions are required.
c. increasing the frequency of firing of only the strongest motor units.
d. active control over the muscle spindle.
217. Tension in large muscles in vertebrates is controlled primarily by
controlling the
*a. number of active motor units.
b. frequency of firing of motor units.
c. firing of the large motor neurons first, followed by the small ones.
d. amount of transmitter released by each action potential, through
facilitation.
218. The size principle of muscle activation states
a. the biggest muscles are used first.
b. the smallest muscles are used first.
*c. the smallest motor neurons are excited first.
d. the largest motor neurons are excited first.
219. Operation of the size principle during the contraction of a human muscle
will result in
*a. an orderly recruitment of motor units as tension requirements increase,
with some units always being activated before others.
b. a recruitment of large motor units (those with the largest numbers of
muscle fibers) before small ones.
c. a sharing of load (during a maintained, constant contraction) between
large and small motor units.
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